1. Field of the Invention
The invention concerns an infrared light detector with high resolution and high structural density.
2. Description of the Prior Art
It is known to use infrared light to detect gas. With a suitable light source the gas to be detected is exposed with infrared light, wherein a portion of the infrared light is absorbed by the gas such that a residual light remains. The residual light can be measured with an infrared light sensor with which the wavelength range and/or the intensity of the residual light can be detected and correspondingly transduced into an electrical signal. Given a suitable evaluation, the type and content of the detected gas can be concluded based on the electrical signal.
The infrared light detector has a number of sensor chips that are arranged in a grid arrangement on a carrier membrane. The sensor chips are conventionally produced from a layer with pyroelectrically sensitive material, for example lead-zirconate-titanate (PZT). The carrier membrane is conventionally produced from silicon. The sensor chips are electronically wired with electrodes that, for example, are produced from platinum or a chromium-nickel alloy absorbing the infrared radiation.
The sensor chips are attached to the carrier membrane and in contact with it in a thermally conductive manner. The sensor chips are therefore coupled with one another in a thermally conductive manner via the carrier membrane. The thermal conduction through the carrier membrane from one sensor chip to the other sensor chip is defined by the coefficient of thermal conductivity of the carrier membrane and the thickness of the carrier membrane. If one of the sensor chips is exposed with the infrared light, the sensor chip is heated due to absorption of the infrared light by the sensor chip. The heat is transferred from the sensor chip to the carrier membrane via thermal conduction, wherein a temperature equalization occurs in the carrier membrane and the other sensor chips. A sensor chip that, for example, is not activated due to a momentary infrared light exposure is heated by a different sensor chip located in its surroundings, which has the consequence of an unwanted activation of this sensor chip. This effect is known as thermal crosstalk, and it is desired that it be suppressed as much as possible in an infrared light detector so that the infrared light detector has a high resolution.
It is known to reduce the negative influence of the thermal crosstalk in that the distance between the sensor chips is chosen to be as large as possible. It is thereby achieved that the heating of a sensor chip by adjacently arranged sensor chips can remain within a tolerable range given a provided temperature gradient in the carrier membrane. However, this measure has the disadvantage that the areal extent of the infrared light detector is too large due to the large distances between the sensor chips.